The effects of active immunization against GnRH on testicular development, feedlot performance, and carcass characteristics of beef bulls

摘要: The objective was to determine the effects of a recombinant fusion protein anti-GnRH vaccine on testicular development, feedlot performance, and carcass quality beef bulls. Crossbred bulls (n = 58, average weight 306 kg, 9 mo age), were randomly allocated two groups received either an (GnRH) or placebo (Control) by intramuscular injection d 0, 56, 112. There group (P < 0.01; as percentage Control) (53%), daily sperm production (40%), epididymal reserves (16%). x time interactions 0.0001) for scrotal circumference serum testosterone concentrations; at slaughter, in GnRH had smaller 0.05) (28.3 vs 33.9 cm) lower concentrations (2.2 8.6 ng/mL) than those Control group. Average gain, feed intake, efficiency not different between treatments during backgrounding phase (d 0 84). During finishing 98 182), ADG greater (1.69 1.42 kg/d), (6.9%; P 0.01). However, numerically better (6.12 7.08 kg DMI/kg gain; 0.23) shear force values ribeye that 16% 0.14) bulls, warranting further investigation. Vaccinating against suppressed function, with growth characteristics similar expected steers.